Tyler DeWitt uses YouTube videos to teach chemistry and other science subjects to hundreds of thousands of students around the world each week. The holder of a PhD in chemistry from Massachusetts Institute of Technology, he believes that the best way to give young people a love of science is to make learning it fun. Tyler works solo, shooting his videos in a makeshift studio crammed into a tiny bedroom in his New York apartment. Before he starts filming, he spends hours reading textbooks and taking notes. Next, he distills the information he has gathered into a series of concise points. Then, using marker pens, scissors, tape and coloured paper, he makes his visual aids. After rehearsing a new lesson to get it exactly the right length, he arranges his lights, microphones and cameras, then films himself speaking to an empty room. His videos use a split-screen format: his hands and visuals in one part of the screen, his body and face in the other. Allowing students to look back and forth between his hands and his face recreates the feel of one-on-one tutoring, he says. Making one video can take dozens of takes over several days. “I spend a lot of time talking into a camera, all alone” says Tyler. “But when I’m recording a lesson I try to imagine the students who watch my videos from all over the world. It’s intimidating, but also amazing.”